Kinetic studies on the thermal decomposition of calcium carbonate

Abstract

Kinetic studies have been made of the thermal decomposition of precipitated calcium carbonate, powdered calcite, and regular fragments of calcite crystals. The powdered materials were examined in the form of pellets, which were prepared by compacting the powder to about 70% of its theoretical density. The work was done at one atmosphere of pressure in a flow of air containing various amounts of carbon dioxide. It was observed that the decomposition of the pellets, which were prepared in a variety of shapes, was characterized by the same advancing interface mechanism as that observed for single specimens of crystal fragments. When the rates of decomposition were normalized for the change in of interfacial area accompanying decomposition, it was possible to correlate the observed rates of decomposition for a variety of pellet shapes, and to relate these rates, as a function of particle size and pellet roughness, to the rates of decomposition of large fragments of calcite crystals. The activation energy for the decomposition reaction was found to be 40.6 kcal./mole. At a constant temperature, the decrease in reaction rate with increasing carbon dioxide pressure was found to be proportional to the difference between the equilibrium dissociation pressure and the back pressure of carbon dioxide. A reaction mechanism based on diffusion through a constant thickness of active calcium oxide is suggested.

Some considerations regarding the kinetics of solid-state reactions

“…It is important to note that the equation is valid for samples with spherical geometry. This idea of the use of spherical samples can be found in the papers of several authors [23,[37][38][39].…”

The measurement of meaningful kinetic parameters for solid state decomposition reactions

“…Experimental confirmation that the relationship between the rate constant and the presseure of product gas is of the form given in Eq. (43), has been obtained by several workers [6][7][8][9], thus we can have some confidence that the general thrust of the arguments presented here must be correct.…”

COORDINATION COMPOUNDS OF OLEFINS WITH ANHYDROUS SILVER SALTS: III. KINETICS OF THE GAS–SOLID REACTION PRODUCING AgBF4•2C3H6

“…I t has been reported by several investigators (6,11) that, for ltinetically controlled reactions, the rate is often directly proportional to the difference between the imposed pressure and the equilibrium dissociation pressure of the con~pound, i.e. for combination reactions to P -P,.…”

“…I t is probable then that the temperature dependence of ks is simply that of the adsorption of propylene as suggested by eq. [6].…”